Cargo containers, such as shipboard cargo containers and cargo trailers used in the trucking industry, are often tracked using small tracking devices attached to the containers. These tracking devices typically incorporate a GPS module for determining the location of the container and a wireless communication module, such as a cellular or satellite modem, to transmit the location information to a central monitoring station. The tracking devices are usually attached to the containers using screws or “peel and stick” adhesive pads.
Such tracking devices are vulnerable to unauthorized removal, such as by thieves who have stolen the cargo container to which the tracking device is attached. Typically, if a thief is aware of the presence of the tracking device, the thief will remove the device at the first opportunity and discard it to prevent tracking of the stolen container. With conventional tracking devices, removal is fairly straightforward, and may involve only removing a few screws or peeling away an adhesive pad.
Typically, unless the tracking device is damaged during the removal process, the device continues to transmit its location to the central monitoring station with no indication that the device has been removed from the container. In such a situation, without other independent information regarding the theft or a geofence trigger event from the tracking device, the central monitoring entity may have no indication that the container has been stolen.
What is needed, therefore, is a system for sensing removal of a tracking device from a container or other asset, and for transmitting a notification signal to a central monitoring station upon such removal.